Legitimate massage therapists are tired of them and law enforcement officials see them as potential venues for human trafficking.

Now, the Florida Legislature is also flexing its muscle in the fight against the growth of adult-oriented massage establishments, places whose marketing and signage skews closer to adult entertainment than therapeutic well-being.

In South Florida, they're known for their blacked-out windows, neon signs, late-night hours, and sexually suggestive postings in online classified ads. Many are listed on web sites that cater to the men who seek out erotic massages.

Observers worry that in some of these businesses, victims are being forced to perform sexual acts against their will.

That rationale, based on numerous cases of sexual exploitation in brothels posing as massage establishments across the U.S., is now official in Tallahassee. In the recent session, lawmakers unanimously passed massage-specific legislation viewed by stakeholders as an important step — even if some say the legislation doesn't go far enough.

Among the proposed new rules: no massage establishment would be permitted to open between midnight and 5 a.m., although there are exceptions for certain legitimate scenarios like spas in hotels and massage therapists who work at airports, where pilots often get massages after long flights.

It would also be illegal to have anybody living on the premises of massage establishments. This reflects the concern among law enforcement that, in some businesses, traffickers are imprisoning workers in back rooms.

The Sun Sentinel saw what appeared to be a bedroom, packed with clothes and other personal belongings, in one Broward County massage establishment in late 2012. The female workers said nobody was living there, that it was a break room.

Like any storefront massage establishment in Florida, that business was licensed by the state Department of Health. This is the case for the majority of the late-night massage parlors — because it's illegal to advertise massage services in the state without displaying a license number.

But recent cases have called the licensing system into question.

In 2012, state health regulators suspended the licenses of 161 massage therapists after they were accused of buying phony credentials from a former Florida College of Natural Health employee, and then using those credentials to become licensed. Since then, the board that governs massage therapists in the state has revoked or accepted the forfeiture of the licenses of dozens of people — most of them Asian women.

The new legislation hadn't yet been sent to the governor's office, so it has yet to be signed by Gov. Rick Scott. Scott's press secretary, Jackie Schutz, said in an email that when it does, "We will review it."

"I am confident that he will sign it," said Rep. Dave Kerner, D-Lake Worth, the sponsor of the house bill.

Kerner, who said he has no indication of the governor's intentions, put the massage issue in the same context as the recently banned online gaming arcades.

"I would say that over the last five years I've really noticed an increase in massage establishments and Internet cafes in my district," Kerner said.

Adriane P. Reesey, community specialist with the Broward Sheriff's Office and chairperson of the Broward Human Trafficking Coalition, called the legislation a "good start."

"The fact that the legislation got this far is indicative of the work that's been done on the ground by the people who have been working hard to bring the issue of human trafficking to the forefront," Reesey said.

Other stakeholders are keeping an open mind, even if they aren't enthused about the hours limitation or the lack of more stringent background checks.

Alex Spassoff, legislative chairman of the Florida State Massage Therapy Association, said he welcomes the legislative effort. But he said the association would have preferred to see more thorough background checks for license applicants — an expense that would have cost each applicant about $80, he said. It was unsuccessful, he said, because Florida lawmakers seem reluctant to impose new business-related costs and taxes.

"The better way to eliminate it would be to keep these people from getting in the door," said Spassoff, who is based in Tampa.

And although there have been several recent arrests, including eight women arrested at establishments in Tamarac and Hallandale Beach last month, the potential for human trafficking in the illegitimate massage industry is also a concern across the country, law enforcement officials say.

"I think the big change has been our understanding that it's possible that these women are doing this work against their will," said David Rogers, supervisory special agent at the FBI's anti-human trafficking program in Washington.